X-Ray Structural Analysis of Ester and Ether Derivatives of 4,5-endo,endo-9,10-Dimethanonaphthalene-11-ol: Evidence for π - σCO* Participation in the Ground State

2008 ◽  
Vol 61 (12) ◽  
pp. 956 ◽  
Author(s):  
Wesley Jackson ◽  
Jonathan M. White
Keyword(s):  
Structural Analysis ◽  
Weak Interaction ◽  
Ground State ◽  
System Analysis ◽  
Diels Alder ◽  
Oxygen Probe ◽  
Structural Effects ◽  
X Ray ◽  
Carbon Carbon Bond ◽  
Derivatives Of

Application of the variable oxygen probe to the polycyclic alcohol 11 and its crystalline ester and ether derivatives provides evidence for a weak interaction between the neighbouring homo-allylic π-system and the C–OR bond; there is no evidence for interaction with the remote π-system. Analysis of the carbon–carbon bond distances in 11–14 reveals structural effects consistent with the manifestation of one of the two possible retro-Diels–Alder reactions in the ground state.

X-ray Structural Analysis for the Prediction on the Nature of the Retro Diels - Alder Pathway: Concerted or Stepwise. Structural Studies on Nitrosobenzene Cycloadducts

2009 ◽  
Vol 62 (12) ◽  
pp. 1695 ◽  
Author(s):  
Jesse Roth-Barton ◽  
Jonathan M. White
Keyword(s):  
Structural Analysis ◽  
Crystal Structures ◽  
Diels Alder ◽  
Structure Parameters ◽  
Structural Studies ◽  
Structural Effects ◽  
X Ray ◽  
Early Stages ◽  
Clear Differentiation

Crystal structures of nitrosobenzene cycloadducts 5–7 reveal structural effects consistent with the early stages of the retro Diels–Alder fragmentation. There is a clear differentiation between the structure parameters of cycloadduct 5, which reacts by a concerted synchronous pathway and that of cycloadduct 6, which must react by a two-step pathway. Based on these data, cycloadduct 7 is predicted to react by a highly asynchronous or two-step pathway.

The conformational preference and barrier to internal rotation of an equatorial 3,5-dichlorophenyl group by the J method. Derivatives of cyclohexane, 1,3-dithiane, 1,3-dioxane, and 1,3-dioxolane

1979 ◽  
Vol 57 (3) ◽  
pp. 355-359 ◽  
Author(s):  
Ted Schaefer ◽  
Walter Niemczura ◽  
Werner Danchura
Keyword(s):  
Magnetic Resonance ◽  
Molecular Mechanics ◽  
Internal Rotation ◽  
Phenyl Ring ◽  
Proton Magnetic Resonance ◽  
Conformational Preference ◽  
Molecular Mechanics Calculations ◽  
X Ray ◽  
Carbon Carbon Bond ◽  
Derivatives Of

We report the preparation and the analysis of the phenyl ring proton magnetic resonance spectra of 3,5-dichlorophenylcyclohexane and of the 2-(3,5-dichlorophenyl) derivatives of 1,3-dioxane, 1,3-dithiane, and 1,3-dioxolane. With the exception of the dioxolanes these compounds exist predominantly as the equatorial isomers. The J method is used to show that the phenyl moiety prefers the conformation in which the α C—H bond lies in the phenyl plane. The predominantly twofold barriers to rotation about the carbon–carbon bond between the two ring systems are 2.0 ± 0.3, 0.4 ± 0.2, 2.2 ± 0.3, 0.85 ± 0.3 kcal/mol for these compounds, in the order given above. The low value for the barrier in the 1,3-dioxane derivative agrees reasonably well with molecular mechanics calculations and with the results of calorimetric and X-ray studies on equatorial 2-phenyl-1,3-dioxane.

Application of the Variable Oxygen Probe to Determine the π-Electron Donor Ability of the Alkyne Group

2014 ◽  
Vol 67 (12) ◽  
pp. 1866 ◽  
Author(s):  
Benjamin L. Harris ◽  
Jonathan M. White
Keyword(s):  
Low Temperature ◽  
Electron Donor ◽  
Oxygen Probe ◽  
X Ray ◽  
X Ray Crystallography ◽  
Donor Ability ◽  
Structural Database ◽  
Derivatives Of ◽  
Electron Demand ◽  
Electron Donor Ability

Eight ester and ether derivatives of propargyl alcohol with varying electron demand were structurally characterised using low temperature X-ray crystallography, these were combined with seven derivatives obtained from the Cambridge Structural Database. Variable oxygen probe analysis of these derivatives provided evidence that the ethynyl substituent is a relatively weak π-electron donor, and is a slightly less effective donor than the C–C bond of an ethyl substituent.

Rigid five-coordinate diorganotin derivatives of oxalic acid diamides, studied by 119Sn-NMR and X-ray structural analysis

2000 ◽  
Vol 604 (2) ◽  
pp. 229-233 ◽  
Author(s):  
Rosalinda Contreras* ◽  
Victor M Jimenez-Perez ◽  
Carlos Camacho-Camacho ◽  
Marisol Güizado-Rodriguez ◽  
Bernd Wrackmeyer*
Keyword(s):  
Structural Analysis ◽  
Oxalic Acid ◽  
X Ray ◽  
119Sn Nmr ◽  
Derivatives Of

Probing the Ground-State δ Effect of Group 14 Metal Substituents. X-Ray Structures of cis- and trans-4-Trimethylmetal-Substituted Cyclohexyl p-Nitrobenzenesulfonates

1998 ◽  
Vol 51 (7) ◽  
pp. 555 ◽  
Author(s):  
Alison J. Green ◽  
Victor Van ◽  
Jonathan M. White
Keyword(s):  
Low Temperature ◽  
Ground State ◽  
Structural Studies ◽  
Structural Effects ◽  
Group 14 ◽  
X Ray ◽  
Bond Interaction ◽  
Cis And Trans

Accurate low-temperature X-ray structural studies on trans-4-trimethylsilylcyclohexyl p-nitrobenzene- sulfonate (31) and cis- and trans-4-trimethylstannylcyclohexyl p-nitrobenzenesulfonates (32) and (33) failed to demonstrate the presence of any significant structural effects due to a σM-C-σC-C-σ*C-O through-bond interaction between the C–M σ donor orbital and the σ*C-ONs acceptor orbital.

Synthese, Koordinationschemie und Ligandeneigenschaften sekundärer Phosphane R(Ar*)PH mit sperrigen aromatischen Resten - Molekülstruktur von Ph(2,4,6-iPr3C6H2)PH, (2,4,6-iPr3C6H2)2PH und ClAu[PhP(2,4,6-Bu3C6H2)H] / Synthesis, Coordination Chemistry and Ligand Properties of Secondary Phosphines R(Ar*)PH with Bulky Aromatic Substituents - Molecular Structure of Ph(2,4,6-iPr3C6H2)PH, (2,4,6-iPr3C6H2)2PH and ClAu[PhP(2,4,6-tBu3C6H2)H]

1996 ◽  
Vol 51 (8) ◽  
pp. 1183-1196 ◽  
Author(s):  
David J. Brauer ◽  
Frank Bitterer ◽  
Frank Dörrenbach ◽  
Gisbert Heßler ◽  
Othmar Stelzer ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Subsequent Reduction ◽  
Coinage Metal ◽  
X Ray ◽  
Modeling Techniques ◽  
Electronic Parameters ◽  
Bulky Ligand ◽  
Derivatives Of ◽  
Nmr Signals ◽  
Secondary Phosphines

The secondary phosphines R(Ar*)PH(R = Me, iPr, Ph, Mes, Ar*) (2a-2h) with bulky aromatic substituents Ar* (Ar* = 2,3,6-R′ 3C6H2, R′ = iPr, tBu) are obtained in good yields by reaction of RPCl2, PCl3, PBr3 or Ar*P(Cl, Br)2 with 2,4,6-tBu3C6H2Li or 2,4,6- iPr3C6H2MgBr and subsequent reduction of the intermediate halophosphines R(Ar*)PX(X = Cl, Br) with LiAlH4. The X-ray structural analysis of Ph(2,4,6-iPr3C6H2)PH (2g), space group P1, shows P-C-distances of 1.824(1) and 1.838(1)Å. The lithium derivatives of 2a-2c are monomeric in solution as indicated by the 1 :1 :1 : 1-quartet 7L i - 31P fine structure of the 31P {1H} NMR signals at low temperatures. 2a-2c and 2f-2h form Ni(0) and Fe(0) complexes (CO)3NiL (6a-6f) and Fe(CO)4L (7a-7d), respectively. The Tolman electronic parameters of the bulky ligands are almost identical. Within the series 2a-2h the spatial shielding of the P atoms has been estimated using advanced molecular modeling techniques. The bulky ligand 2c forms coinage metal complexes [C u(CH3CN)2(2c)2] [PF6] (8), Cu2Cl2(2c)2 (9) and Cl-Au(2c) (10). While 10 is monomeric in solution, in the solid state it forms pairs of head to tail oriented monomers with almost linear Cl - Au - P skeletons (Cl - Au - P 175.47(9)°) as shown by an X-ray structural analysis.

Competitive Intramolecular Diels - Alder Reactions of bis-α,β-Unsaturated Ester Derivatives of Enzymatically Derived and Enantiopure cis-1,2-Dihydrocatechols. Enantiodivergent Synthesis of Monochiral Bicyclo[2.2.2]oct-2-enes

2003 ◽  
Vol 56 (9) ◽  
pp. 861 ◽  
Author(s):  
Martin G. Banwell ◽  
Cai Chun ◽  
Alison J. Edwards ◽  
Markus M. Vögtle
Keyword(s):  
Natural Products ◽  
Single Crystal ◽  
Building Blocks ◽  
Diels Alder ◽  
Unsaturated Ester ◽  
Enantiomerically Pure ◽  
X Ray ◽  
Derivatives Of ◽  
Natural Products Synthesis

bis-Crotonate and related α,β-unsaturated ester derivatives of readily available and enantiomerically pure cis-1,2-dihydrocatechols engage, upon heating in refluxing toluene, in two competitive intramolecular Diels–Alder reactions to give varying mixtures of chromatographically separable and pseudo-enantiomeric bicyclo[2.2.2]oct-2-enes. Such adducts, many of which have been characterized by single-crystal X-ray analysis, are likely to serve as useful building blocks in natural products synthesis.

Structure Correlation Study of the Beckmann Rearrangement: X-ray Structural Analysis and 13C–13C 1-Bond Coupling Constant Study of a Range of Cyclohexanone Oxime Derivatives

2012 ◽  
Vol 65 (7) ◽  
pp. 905 ◽  
Author(s):  
Shin Dee Yeoh ◽  
Benjamin L. Harris ◽  
Tristan J. Simons ◽  
Jonathan M. White
Keyword(s):  
Bond Distance ◽  
Correlation Study ◽  
Beckmann Rearrangement ◽  
Coupling Constants ◽  
Structural Effects ◽  
X Ray ◽  
Early Stages ◽  
Carbon Carbon Bond ◽  
Oxime Derivatives ◽  
Electron Demand

The X-ray structures of a range of oxime derivatives (1 and 4), of cyclohexanone and 4-tert-butylcyclohexanone, where the electron demand of the oxygenated substituent on the oxime nitrogen (OR) is systematically varied were determined. It was established that as the OR group becomes more electron demanding, then the N–OR bond distance increases, consistent with the early stages of bond breakage. Concomitant with this structural effect was a noticeable closing up of the N1–C1–C2 bond angle, consistent with the early stages of migration of the antiperiplanar carbon onto the nitrogen substituent. These structural effects are consistent with the manifestation of the early stages of the Beckmann rearrangement in the ground state structures of these oxime derivatives. The carbon–carbon bond distances of the participating carbons in this rearrangement, however, did not vary in a systematic way with the electron demand of the OR substituent, suggesting that the structural effects are too small to be detected using X-ray crystallography. However, the 13C–13C 1-bond coupling constants, which are sensitive to the effects of hyperconjugation, were shown to vary in a systematic way with the electron demand of the OR substituent. Structural effects in the oxime 5 derivatives of 2,2-dimethylcyclohexanone, a substrate that is prone to Beckmann fragmentation rather than Beckmann rearrangement, were similar but smaller in magnitude.

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